The present invention relates to an apparatus and method for packing cigarettes into cigarette packages sealed with pre-applied adhesives. More particularly, the present invention relates to manufacturing cigarette packages in which the packaging stock (such as pack labels) is coated with adhesive before it is supplied to the packaging machine and the machine provides means for activating the adhesive, and preferably setting the adhesive after it has been activated. Known wet-glue packaging machines may be modified to practice the present invention by removing or disabling the wet-glue application apparatus and adding apparatus as required to activate and set the pre-applied adhesive.
Cigarette packing machines are widely used in high speed cigarette manufacturing operations. In a typical commercial wet adhesive ("wet-glue") packing machine, cigarettes pass through successive processing steps to be formed into packs. Two types of machines are widely used--turret-type wet-glue machines and mandrel-type wet-glue machines. Water or other solvent based or wax based adhesives commonly are used. A typical soft cigarette pack manufactured by such machines comprises an internal liner, an external label, which typically is made of coated paper, and a closure stamp.
In general, turret-type wet-glue packing machines can be used to form a soft cigarette packs in several steps. First, a bundle of cigarettes, typically 20 in number, is formed. The cigarette bundle then passes among a number of processing turrets to form a pack. In this processing, a foil coated paper liner ("foil liner") is wrapped around the bundle and its ends are folded. Then, a label is wrapped around the bundle, and the portion corresponding to the bottom of the bundle is folded. The labels may be supplied to the machine on spools, or in pre-cut stacks. If spools are used, then the packing machine generally will include apparatus to cut individual labels as the spool is unwound. Before a label is wrapped around a bundle, wet glue is applied to the label. Typically the glue is applied at an edge corresponding to the sideseam of a cigarette pack and at another edge, corresponding to the folded over bottom of the pack. The wet glue is set after the label is wrapped around the bundle by holding it in place until the wet-glue has dried; heat may be applied to accelerate drying.
Turret wet-glue cigarette packers are widely known and exemplary versions are described in U.S. Pat. Nos. 3,628,309 and 3,948,115, both of which are assigned to G. D. Societa per Azioni, Via Pomponia 10, 40100 Bologna, Italy, which also sells commercial turret-type wet-glue packers under various model designations, including GDX-1 and GDX-500. U.S. Pat. No. 3,848,115 is incorporated herein in its entirety by reference. The GDX-1, which is generally described in U.S. Pat. No. 3,948,115, is used for illustrative purposes in the description of the present invention that follows. The GDX-1 incorporates apparatus for the application of glue to the labels comprising a glue dauber assembly, glue roller, scraper assembly, glue pot, glue fill assembly and glue pot sensor. The GDX-1 also incorporates four processing turrets. In operation, the cigarette bundles are passed from turret to turret, each turret performing predetermined processing functions. The fourth turret functions to finish the folds on the bottom of the label in conjunction with an insertion finger (also called a "leaf spring") and then to set the glue on the bottom panel by operating in conjunction with a generally flat and semi-circular heating assembly. The generally flat face of the heating assembly has a flat raised portion that is designed to contact the pack bottoms and thereby set the glue by application of heat and pressure. In addition, the GDX-1 packer incorporates an exit ramp, which the wrapped cigarette bundles enter after the fourth processing turret. The exit ramp comprises a heater and pressure plate, which operate in conjunction to set the sideseam glue.
Mandrel-type wet-glue packing machines generally differ from turret-type machines as follows: The foil liner and label are wrapped around a hollow mandrel and the bottom of the foil liner and label are folded; the cigarettes are inserted into the hollow center of the mandrel; the cigarettes and packaging components are removed from the mandrel and the top folds are made; the pack is then transferred to a heating belt where the pack is subjected to heat, which may aid in drying the wet glue.
Wet-glue packaging machines possess a number of known disadvantages. One such disadvantage is slippage. Slippage occurs when opposing portions of the packaging stock, which are supposed to be sealed in a predetermined alignment, move with respect to each other before the wet glue is set such that the desired alignment is not achieved. As packers are operated at higher speeds, the occurrence of slippage tends to increase. Slippage therefore is undesirable because when it occurs, the resulting packs may be improperly sealed (impairing the shelf-life of the cigarettes contained and impairing the ability of the label to hold the packs together), the seals may not be properly registered; the label may be wrinkled or scalloped and the labels may have a sloppy or otherwise displeasing appearance.
Clogging is another known disadvantage of wet-glue packaging machines. Clogging occurs when the apparatus used to apply the wet glue to the packaging stock becomes blocked. Clogging also occurs as wet-glue is transferred from the glue application apparatus to downstream processing apparatus, thereby causing the downstream processing apparatus to become clogged. When clogging occurs, the machine must be stopped and cleaned by an operator--resulting in productivity loss.
Smearing is a further known disadvantage of wet-glue packaging machines. Smearing occurs, by way of example, when glue seeps out from glued seams, when it bleeds through the stock, when it smears and when it slings. Smeared packages can have a dirty and otherwise undesirable appearance.
Yet another disadvantage of wet-glue packaging machines is due to product loss from machine stoppages. As with many complex machines, wet-glue machines often are stopped. Machines may be stopped, for example, for de-clogging or other maintenance, re-supply and personnel changes. Manufacturing runs often may continue uninterrupted for less than 5-15 minutes. Each time a wet-glue machine is stopped, product may be lost because the glue that has been applied to packaging stock that are in processing dries during the stoppage. In both turret-type and mandrel type of wet-glue packers, packs can be lost on the heated exit apparatus. For example, when a typical turret-type wet-glue packer stops, the heating plate on the exit ramp stays hot. Thus, when the packer stops, the packs on the exit ramp can be degraded or burned.
A further disadvantage of wet-glue packaging machines is a lack of flexibility regarding the placement of adhesive. In the wet-glue machines, glue is applied with the glue daubers. The packaging stock is directed to the glue daubers by guides. The glue placement by the daubers must avoid the guides. In addition, the processing apparatus must be constructed such that mechanical elements downstream of where the glue is applied do not contact the wet glue.
Still further disadvantages of wet-glue packaging machines are difficulty in controlling the amount of glue that is applied, high viscosity of the glue itself, glue build-up along guides and frequent maintenance required by the glue application apparatus.